The utilization of compression molding of organic thermoplastic materials has not progressed much beyond the single mold stage. It is known that a heated gob of organic thermoplastic material may be deposited in a molding cavity and a plunger then moved into co-operation with the cavity opening to close the cavity and effect the compression molding of the heated gob to conform to the configuration of the molding cavity. When large quantities of thermoplastic articles are required, the prior art has heretofore resorted to multi-cavity injection molding. The greater the number of cavities, or the size of the article, the greater was the clamping force required to hold the mold together, hence the machine became larger and more expensive and the mold cost almost prohibitive. At the same time, the multi-cavity injection molding process is inherently an intermittent process and requires a significant portion of each molding cycle for the molds to remain in the closed position until the injection-molded articles are sufficiently cooled to permit the molding cavities to be open.
There is therefore, a need for an efficient, low-cost continuously operating molding apparatus for effecting the large quantity economic production of a variety of thermoplastic articles by the compression molding technique.